This invention generally relates to slider-operated plastic zippers intended for use in reclosable pouches, bags or other packages. In particular, the invention relates to methods and apparatus for supporting zipper tape during slider insertion.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies often include a plastic zipper and a slider. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, etc. Reclosable bags having slider-operated zippers are generally more desirable to consumers than bags having zippers without sliders because the slider eliminates the need for the consumer to align the interlockable zipper profiles before causing those profiles to engage.
Conventional slider-operated zipper assemblies typically comprise a plastic zipper having two interlocking profiles and a slider for opening and closing the zipper. In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger at one end that is inserted between the profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction. Other types of slider-operated zipper assemblies avoid the use of a separating finger. For example, U.S. Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually interlockable profiled structures, portions of which form a fulcrum about which the profiled structures may be pivoted out of engagement when lower edges of the bases are forced towards each other.
An improvement in sliders is disclosed in U.S. patent application Ser. No. 10/096,409 filed on Mar. 11, 2002 and entitled “Insertion Apparatus for Attaching Sliders onto Zipper Bags and Film”. This slider can be inserted on the zipper in a manner such that the zipper will be secured in the slider. As a result, during an opening of the reclosable bag the interlocking closure elements of the zipper will not unintentionally re-engage within the slider. For example, a re-engagement of the interlocking closure elements could occur when the zipper opening end of the slider is pushed toward a closed zipper park position. Such a re-engagement can occur during operation of the zipper or if the slider is inserted too far from a slider end stop on the zipper. By reducing the possibility of unintentional re-engagement of the interlocking members of the profiles, production of defective bags is reduced.
U.S. patent application Ser. No. 10/096,409 discloses a slider insertion apparatus comprising an activator that opens a first portion of a zipper tape, a pusher that inserts the slider onto a second portion of the zipper tape, and a zipper guide that holds a third portion of the zipper tape closed. The zipper guide and the activator with pusher are manufactured to facilitate forward movement of the zipper tape within the slider insertion apparatus; to properly position the profiles of a section of zipper for slider insertion; and to secure an adjacent section of the zipper when the slider is inserted. A loading rack with a supply of sliders may be part of the slider insertion apparatus, with the loading rack being a mechanically attachable device or module.
In the slider insertion process, a closed zipper tape is guided by a pair of opposing grooves formed in opposing parts of a zipper guide to an insertion point under the activator with pusher. An activating fork of the activator with pusher offsets the interlocking members in a section adjacent to where the slider is inserted. The slider is inserted onto the interlocked zipper tape by the pusher. The interlocked zipper tape is supported in the area where the slider is inserted by a pair of guide blades.
The above-described grooves in the zipper guide form a passageway for translation of a zipper tape along its longitudinal axis. Because the grooves are configured and arranged to define a cross-sectional passage that generally conforms to the profile of the closed zipper tape, e.g., an A-shaped profile, the zipper tape has only one degree of freedom, namely longitudinal translation. A zipper guide with a narrow passageway for the zipper profile only will not allow passage of a slider inserted on the zipper tape. Therefore such a zipper guide cannot be used in cases where zipper activation occurs behind the inserted slider and the zipper guide holds the zipper tape in front of the slider insertion area. Also, a static zipper guide (having an unchanging guideway for the zipper tape) cannot be used in cases where dual sliders are inserted on respective zipper lengths by respective slider insertion devices and then the zipper tape is advanced or indexed two zipper lengths, each zipper length having a slider inserted thereon. In order to advance the zipper tape in these cases, the size of the passageway of the zipper guide must be increased to allow passage of a slider through the zipper guide station.
Thus there is a need for a zipper guide apparatus having different states, wherein the zipper tape is held securely in a zone adjacent the slider insertion zone during slider insertion in a first state and is not held securely in the adjacent zone and allows a slider to pass through during zipper tape advancement.